Wind turbines have received increased attention as a renewable energy source for generating electricity. Wind turbine power systems, such as doubly fed induction generator (DFIG) power systems, often include a power converter with a regulated DC bus. For example, a DFIG power system can include a power converter with a rotor side converter and a line side converter coupled together via a DC bus.
In a typical configuration, the rotor side converter and the line side converter can each include a plurality of bridge circuits, which can include switching devices, such as insulated gate bipolar transistors (“IGBTs”). The IGBTs or other switching devices in the rotor converter can be switched to convert AC power from the rotor of the DFIG to a DC power, which can be provided to the DC bus. The IGBTs or other switching devices in the line side converter can similarly be switched to convert the DC power from the DC bus to an AC power, such as a synchronous AC power, which can then be provided to an electrical grid.
However, the DFIG power system may be exposed to transient voltages, such as during grid disturbances, which can cause oscillations of power into and out of the power converter. This can cause the DC bus voltage to oscillate. In a typical protection scheme, when the DC bus voltage exceeds an overvoltage threshold, the power converter is shut down in order to protect the switching devices. However, shutting down the power converter to protect the switching devices can limit the availability of the DFIG power system, and reduce the amount of power generated by the DFIG power system.